The Casimir force between an ellipsoid and a plate can be tuned by using the combination of anisotropic materials and nonlinear materials exhibiting the AC Kerr effect. The force was obtained numerically by using the FDTD method, based on the Maxwell's stress tensor. The results indicate that the force can be significantly varied by changing the intensity and location of the laser, as well as the properties of material. The sensitive changing between ellipsoid and plate structure with different materials' properties provides new possibilities of integrating optical devices into nano-electro-mechanical systems (NEMS).

A planar compact multiband monopole antenna is presented for ultra-slim mobile handsets applications. The proposed antenna operates over 0.885 GHz-0.962 GHz and 1.69 GHz-3.8 GHz frequency bands with -6 dB impedance bandwidth that covers GSM900, GSM1800, GSM1900, UMTS, IMT2100, WLAN, WiMAX along with most of the higher LTE bands of modern mobile phone applications. The radiation characteristics of the antenna is analyzed in term of radiation patterns, peak realized gain, total radiation efficiency, and surface current distribution. The radiation patterns of the proposed antenna is dipole like which is suitable for mobile applications with 73-93% total radiation efficiency. The proposed antenna is investigated in free space as well as in actual mobile environment consisting of mobile plastic housing along with large metallic display screen and battery. No significant effect on the operating bands of the mobile antenna due to the actual mobile environment on the impedance bandwidth is observed. Specific absorption rate (SAR) computation is carried out on human head phantom. The computed values of SAR lie well below the specified limit over 1 g and 10 g of tissues. The parametric analysis is also carried out to understand the effect of the shape parameters.

In this paper, a novel folded metal-plate monopole antenna is presented for indoor digital television (DTV) signal coverage in the 454-1300 MHz band. The proposed antenna consists of a folded metal-plate with two asymmetrical bevels and a shorted pin connecting the metal-plate with a ground plane. The folded structure extends the lower frequency band and reduces the height of the antenna for better application to DTV. Experiment results show that the antenna achieves a bandwidth for |S₁₁| < -10 dB ranging from 454 MHz to 1300 MHz and shows stable radiation patterns in three coordinate planes.

This paper presents a novel method to design filtering power divider with compact size. Based on lumped elements, a novel topology is proposed and theoretically analyzed. The equivalent power splitting circuits and filtering circuits are characterized by even-odd-mode analysis. Closed-form design equations are obtained, and all the unknown parameters can be derived. Meanwhile, two transmission zeros are produced near the passband edges, resulting in high-selectivity quasi-elliptic responses. For demonstration, a filtering power divider is implemented. The circuit operating at 600 MHz occupies only 15 mm × 14 mm.

In this paper, an efficient three-dimensional Laguerre-based finite-difference time-domain (FDTD) method is used to analyze planar circuits. An iterative procedure is introduced to improve the accuracy. Both the time-domain waveforms and the S-parameters are presented. The numerical results show that at the comparable accuracy, the efficiency of the Laguerre-based FDTD method with an iterative procedure is superior to the FDTD method and alternating-direction implicit (ADI) FDTD method.

A novel compact and multiband dipole antenna with a planar fractal-inspired configuration is presented. Several series capacitances and a parasitic element are employed as loading. Results show that the loading improves the impedance matching and enables the proposed antenna to radiate at multiple frequency bands. In addition, the proposed loaded dipole antenna offers a high degree of miniaturization in comparing with the unloaded host dipole antenna. The simulated |S₁₁| response of the proposed loaded dipole antenna shows five distinct resonant bands with the center resonant frequencies of 1.52 GHz, 3.62 GHz, 4.6 GHz, 6.9 GHz, and 9.43 GHz. A fabricated prototype has compact dimensions of the 37 mm × 14 mm × 1.6 mm, and exhibits good agreement between the measured and simulated S-parameters.

A low-profile broadband dual-polarized antenna with high isolation and low cross polarization is presented in this letter. The proposed antenna employs two different feeding mechanisms. On one hand, two out-of-phase probes loaded with two small circular patches make the proposed antenna operate in horizontal mode. On the other hand, two pins connecting two eyebrow-shaped patches and the ground form a magnetic loop which enables the proposed antenna to achieve vertical polarization. By elaborately adjusting the feeding structures, measurements demonstrate that the proposed antenna not only achieves 10-dB return loss bandwidths of 49% (1.7-2.8 GHz) and 28% (2-2.65 GHz) for Port 1 and Port 2, respectively, but also maintains a high isolation better than 32 dB over the entire common frequency band. Meanwhile, within the main lobes, the cross polarization levels, both in E-plane and in H-plane, stay lower than -25 dB for Port 1 and -20 dB for Port 2. In addition, the proposed antenna with a profile of 0.13 achieves the maximum gains of 8.4 dBi for horizontal polarization and 8.2 dBi for vertical polarization.

For coherent jammers to wideband linear frequency modulation (LFM) radar, the ratio between jamming energy and signal energy is always constant. To enhance the jamming to signal ratio (JSR), a two-dimensional (2D) discretized coherent noise jamming (2D-DCNJ) method is first proposed in this paper, where the covering area of the noise jamming results in 2D imaging is limited to a certain shape and further discretized to centralize the jamming energy. Moreover, the idea of weighting is applied to 2D-DCNJ to control the distribution of jamming energy, which can present some particular deceptive characteristics. The relationship between jamming results and modulated noise is analyzed, based on which the procedure of generating the jamming signal is detailed, and the JSR performance is compared with the previous ones. Finally, the validity of the proposed method is demonstrated via numerical simulation.

In this article, a compact dual-band bandpass filter (BPF) using coupled open-loop resonators and an embedded center-grounded stepped-impedance resonator (CGSIR) is proposed. This filter operates at 2.1/5.2 GHz for WCDMA/WLAN applications. The first passband is generated by the proposed CGSIR, and the second one is created by the coupled open-loop resonators. Each passband can be controlled independently by adjusting the dimension parameters of corresponding resonators. Five transmission zeros (TZs) are generated due to the 0° feed structure and signal cancellation effects between electric couplings and magnetic couplings, which improve the filter band-to-band isolation level and skirt selectivity significantly. Moreover, the overall circuit size is very compact due to the embedded configuration. The measured filter performances are in good agreement with the simulated ones.

Based on the conventional finite-difference time-domain (FDTD) method, a novel dual-meshed technique is presented to deal with the underwater detection problems applying in low frequency electromagnetic wave. A transformation surface connecting the coarse cell with the fine cell is implemented by applying a total-field scattered-field source (TSS) technique, which is carried out by two-step FDTD simulation. The ratio of a coarse cell size to a fine cell size can be set as an arbitrary integer, such as N=10. Moreover, it is illustrates that non-physical reflection fields from the TSS surface are avoided by introducing the TSS surface. We have derived, in detail, the update equations of fields on grids of the TSS surface. Three cases of dealing with different underwater electromagnetic problems are discussed. Numerical results show that by analyzing the magnitude and phase of scattered fields from obstacles underwater we can distinguish the category of the obstacles which belongs to either a high resistivity body or a low resistivity body. Therefore, the proposed method provides us an effective tool for analyzing the electromagnetic response of materials underwater.

A novel Quasi-Yagi antenna with low radar cross section (RCS) is proposed in this paper. By using arrow-shaped Koch dipoles as the driver and director and cutting the ground of the antenna, the RCS can be reduced in the operating band of 5 GHz-8 GHz when the incident wave is perpendicular to the antenna plane. Wideband radar absorbing material (WRAM) with frequency selective surface (FSS) is devised to replace the metallic reflect plate of the antenna to reduce the RCS in the maximum radiation direction. The average RCS reduction of the antenna in the frequency band of 3 GHz-12 GHz is 8.0 dB. The simulated and measured results show that there is a considerable RCS reduction of the Quasi-Yagi antenna with WRAM, and the radiation performance is preserved at the same time.

This paper presents a dual-mode stub loaded ring resonator (SLRR) to design a tunable dual-band bandpass filter (BPF) with two independently controllable passbands. The proposed resonator principally comprises a stepped-impedance ring resonator (SIRR) loaded with three stubs and two varactor diodes. Two independently tunable passbands are implemented by employing two varactors to control the dominant even-mode resonant frequency and odd-mode resonant frequency, respectively. Moreover, a new stub loaded double-ring resonator (SLDRR) is proposed to design the second tunable dual-band filter by shorting two stubs of the SLRR. With the same tuning method, the second filter can achieve two independently controllable passbands. In order to suppress the harmonics, defected ground structures (DGSs) are introduced at input and output feeding lines without degrading the passbands characteristics. The simulated and measured results are found in good agreement with each other.

A wideband planar printed quasi-Yagi antenna with band-notched characteristic is presented. The proposed antenna consists of a microstrip-to-slotline transition structure, a gradient driver dipole, and two parasitic strips as directors. Meanwhile, the arms of the driver and two directors are rotated in a certain angle to improve gain. Employing a microstrip-to-slotline transition, a driver dipole and two parasitic strips, the proposed antenna achieves a wide bandwidth for ultra-wideband applications. The driver dipole is connected to the slotline with a coplanar stripline. To avoid the frequency interference from WLAN operating in the frequency band from 5.15 GHz to 5.825 GHz, an L-shape slot etched on the driver dipole element is adopted to achieve notched band ranging from 4.8 GHz to 6.1 GHz. The ground plane is symmetrically added two stubs to implement the lateral size reduction. The measured bandwidth, determined by the reflection coefficient less than -10 dB, covers from 3 GHz to 10.8 GHz. Better than 8.1 dB F/B ratio and the measured antenna gain varying between 4.7 and 8.3 dBi are also achieved in the operating bandwidth excepting in the notched band.

The analysis of waves propagation in homogeneous anisotropic media constitutes a classical topic in every field of science and has been preferentially discussed using locally plane waves. Specific physical quantities and their behaviour laws are really what make the difference. Although the use of Fourier transform enables an approach formally analogous to that of plane waves in linear evolution equations, its application to constitutive equations of inhomogeneous media involves cumbersome convolution products that mask the solution. This paper proposes a polar representation (amplitude and phase) of electromagnetic fields, that appears to be more suitable and provides two sets of equations that can be easily decoupled, reducing the problem to the superposition of two simpler ones. The procedure is based upon the following steps: a) The identification of dispersion equation with Hamilton-Jacobi equation yields the evolution laws of rays and/or wave-fronts. b) From the knowledge of tensor ε(r) at any point r of the wave front (or the ray), the use of the intrinsic character (conjugation relations) of fields, introduced by the authors in a previous work, together with ray velocity or phase gradient (found in the first step) the remaining fields are immediately obtained.

A new compact printed tri-band antenna for WLAN/WiMAX applications is presented. The proposed antenna consists of three inverted L-shaped strips whose geometry looks like a ``bent fork''. These strips are attached to the feed line through a horizontal strip. By optimizing the geometries of the inverted L-shaped strips, distinct resonant points can be effectively created for different frequency bands. The overall size of the proposed antenna is 18 x 33 mm². Simulated and measured results show that the presented antenna can cover 2.5/3.5/5.5 WLAN and WIMAX bands with fairly stable radiation patterns. The antenna structure is simple, small, easily configurable and tuneable, and therefore suitable for practical applications.

In the 150 years that scientists and engineers have used Maxwell's equations to describe electromagnetic phenomena, canonical scattering and radiating problems have played a very important role, providing explanations of and insights into their underlying physics. With the same intent, a variety of active coated nano-particles are examined here theoretically with regard to their ability to effectively enhance or jam(cloak) the responses of quantum emitters, e.g., fluorescing molecules, and nano-antennas to an observer located in their far-field regions. The investigated spherical particles consist of a gain-impregnated silica nano-core covered with a nano-shell of a specific plasmonic material. Attention is devoted to the influence of the over-all size of these particles and their material composition on the obtained levels of active enhancement or jamming. Silver, gold and copper are employed as their nano-shells. The over-all diameters of the investigated coated nano-particles are taken to be 20 nm, 40 nm, and 60 nm, while maintaining the same ratio of the core radius and shell thickness. It is shown that the jamming levels, particularly when several emitters are present, are significantly larger for particles of larger sizes. These configurations are also shown to lead to the largest enhancement levels of the surrounding quantum emitters. Furthermore, for a fixed particle size and for a gain constant that produces the largest enhancement peak at optical wavelengths, it is demonstrated that these larger levels are most notable when the nano-shell is gold.

An asymmetrical coupled-line circuit is proposed to design planar microstrip balun, which has the advantages of compact structure and complex source to complex load impedance transformation. This balun consists of three pairs of coupled lines and two tapped transmission-line stubs. Based on the traditional even-odd mode technique and ABCD parameters, closed-form mathematical equations for circuit electrical parameters are obtained. To demonstrate our design theory, a practical microstrip balun is designed, simulated and measured. The results show that the return loss is larger than 25 dB, the insertion loss S₂₁ (S₃₁) 3.15 dB (3.129 dB), and the output phase difference -180.22˚ at the operating frequency. Good agreements between the simulated and measured results verify our design theory.

Scattering from array antennas is a complicated problem, containing the structural and mode items in nature. The complexities in analyzing the latter one also come from the feeding network that follows antenna unit ports, where active or anisotropy devices may exist. Therefore, it is significant that an efficient method can be constructed to analyze array antenna scattering with arbitrary port reflections. In this work, we address this problem by adopting the S-matrix model for the antenna array, aiming to efficiently and accurately compose the mode scattering in case of arbitrary reflections at feeding ports. In the numerical process, the antenna reciprocity is utilized in obtainning the basis for the scattering composition analysis. In case of various loading conditions, numerical results are presented, showing that the composed scattering results by the S-matrix model agree well with that obtained by direct full scale simulations. Then the methods for obtaining radiation and scattering of a large antenna array based on results of a small array, are reviewed and extended in composing the large antenna array scattering in case of variable loading conditions. And, promising results are obtained.

Two absorbing boundary conditions (ABC's) are derived for the cylindrical MRTD grids. The first one is the convolutional perfectly matched layer (CPML) based on stretched coordinates with complex frequency shifted constitutive parameters, and the other is the straightforward extension of CPML named quasi-CPML (QCPML) as it is no longer perfectly matched for cylindrical interfaces. Unlike the Berenger's PML, the implementations of the two ABC's are completely independent of the host material. Numerical results show that both ABC's can provide a quite satisfactory absorbing boundary condition, and can save more CPU time and memory than the Berenger's PML, while the QCPML has an advantage of CPML at the proposed absorbing performance, CPU time and memory saving. Moreover, it is shown that the QCPML is more effective than the PML and CPML at absorbing evanescent waves.

The present paper describes an integrated approach for design, fabrication and encapsulation of RF MEMS switches in view of the optimal performance subsequent to packaging. `Top and bottom contact' fabrication approaches are explored using different RF MEMS switch topologies. In the `bottom contact package (BCP)' the packaging cap alignment is less critical as compared to the top contact packaging (TCP) approach where contact via is an integral part of the cap. In this case, the connection layout through silicon via holes is independent of the cavity geometry. For the devices under consideration, bulk etched silicon cavity height has been optimized to 50 μm for optimal RF performance e.g. isolation and insertion loss. Parasitic effects of top silicon cap are reduced by altering CPW impedance. Mechanical parameter damping is simulated for different cavity heights and found to be independent from cavity height after 20 μm onwards.